Subj : Re: Strange ".constructor" behaviour -- I don't understand something,
To   : netscape.public.mozilla.jseng
From : Martin Honnen
Date : Tue Oct 04 2005 06:27 pm



Lev Serebryakov wrote:


>>You are not adding some methods you are creating a new prototype object
>>that way.
> 
>   Yes. But not new constructor! 

The object itself has no own property named 'constructor', it is a 
property inherited from the prototype chain.

> So, default prototype object contains
> "prototype" property magically added to it, not to object when it is
> created?

The whole stuff is dynamic, try this example to see

function Class() {}
var c1 = new Class();

var result = [];

result.push('c1.hasOwnProperty("constructor"): ' + 
c1.hasOwnProperty("constructor"));
result.push('c1.constructor.name: ' + c1.constructor.name);

result.push('c1.__proto__.hasOwnProperty("constructor"): ' + 
c1.__proto__.hasOwnProperty("constructor"));

// now change prototype
Class.prototype = { method: function() {} };

var c2 = new Class();
result.push('c2.constructor.name: ' + c2.constructor.name);

result.join('\r\n')


In Spidermonkey the prototype chain is exposed through the __proto__ 
property and you can see that the object created with new Class() does 
not have its own property named 'constructor' but only the one sitting 
in its prototype chain.


-- 

	Martin Honnen
	http://JavaScript.FAQTs.com/

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